This invention relates to a method and apparatus for inspecting any foreign matters or particles by a foreign particles monitor which conducts dust generation evaluation in a mass production line of a semiconductor fabrication process through product wafers.
If any foreign matters or particles exist on a wafer during a semiconductor fabrication process, they will result in defects such as defective insulation and short-circuit of wirings. When a semiconductor device is further miniaturized and if any foreign particles exist in a wafer, they will result in breakdown of a capacitor insulation film and a gate oxide film. These foreign particles are generated and mixed for various reasons and under various conditions. For example, some of them develop from driving portions of a transport unit and from the human body, while the other are produced as reaction products inside a processing apparatus due to a process gas, or are contained in chemicals and starting materials.
The conventional technique of this kind for detecting the foreign particles on the wafer irradiates a laser beam on the wafer, detects scattering light from the foreign particles generated when they adhere to the wafer, compares this detection result with the inspection result of the same kind of the wafer that is immediately before inspected so as to eliminate lie detection resulting from patterns and makes it possible to carry out high sensitivity and high reliability foreign particle inspection, as disclosed in JP-A-62-89336, for example.
Another prior art reference, JP-A-63-135848, discloses a technique which irradiates a laser beam on the wafer, detects scattering light from the foreign particles when they adhere to the wafer, and analyzes the detected foreign particle by analytical technique such as laser photoluminescence or XMR.
One of the main operations for start-up of mass production of LSIs is the operation for clarifying the causes of generation of these foreign particles and for considering an appropriate counter-measure, and detection of the generated foreign particles and analysis of the kinds of elements contained therein give a major key to the clarification of the cause. In a mass production line, on the other hand, the generation of these foreign particles must be detected as soon as possible and any counter-measure must be taken. If a long time passes away from the generation of the foreign particles to the detection of their generation, the number of defects becomes greater and a fabrication yield drops. Therefore, it is imperative to shorten the time from the occurrence of the foreign particle to its detection in order to keep a high fabrication yield. In other words, to maximize the effect of foreign particle inspection, a sampling time of a monitor must be reduced and ideally, real time sampling is preferably made for a mass production line.
However, the prior art references do not clearly distinguish between the state of mass production start-up and the state of a mass production line in a semiconductor fabrication process, and adapt those inspection apparatuses, which are used for the mass production start-up operations, as such to the mass production line. Although the generation of the foreign particles must be detected as soon as possible in the mass production line and appropriate counter-measures must be taken, the conventional inspection apparatuses are of a stand-alone type and inspect the foreign particles by bringing the wafers processed in the production line to the sites of the inspection apparatuses. This means that a long period of time is necessary for the transfer of the wafers and for the foreign particle inspection and hence, the inspection frequency cannot be raised to a sufficient value.
According to the above-mentioned techniques, the inspection apparatuses are great in scale and the foreign particle inspection requires a long time. In order to accomplish a real time monitor by using these conventional apparatuses, therefore, it is necessary to arrange a large number of large-scale apparatuses and this is practically unfeasible. In practice, one wafer has been sampled from one or several lots, or everyday, and this has been a practical limit. If the foreign particle inspection is carried out at such a frequency, the generation of the foreign particles cannot be detected sufficiently rapidly. In other words, the conventional sampling frequency is far apart from the ideal real time sampling. Still another problem with the prior art technique is that a necessary number of monitors must be disposed at sufficient positions in order to reduce the number of man-hours and equipments in the mass production line.
One of the principal operations for the mass production start-up of LSIs is an operation for clarifying the causes the generation of these foreign particles and for taking appropriate counter-measures and to this end, detection of the generated foreign particles and analysis of the kinds of elements will give a major key to the clarification of the causes of the generation of the foreign particles.
U.S. patent application Ser. No. 07/679,317 dated Apr. 2, 1991, entitled "METHOD AND APPARATUS OF INSPECTING FOREIGN MATTERS DURING MASS PRODUCTION START-UP AND MASS PRODUCTION LINE IN SEMICONDUCTOR PRODUCTION PROCESS", which relates to an improvement in the functions such as detection, analysis, evaluation, etc. in the start-up of mass-production operations, is assigned to the Assignee of the present application. The disclosure of the preceding application is herein incorporated by reference.